Contact lens defect inspection using UV illumination

ABSTRACT

A system for detecting defects in a contact lens material comprising: a camera having a lens and a digital image output for inspecting said lens suspended in saline solution, wherein said camera&#39;s digital image output includes only the image produced by light in a color spectrum corresponding to a portion of the spectrum of light produced by fluorescent emission of said lens material; a first Ultra violet light source to illuminate said lens and excite fluorescent emission therein; a first filter to filter the emitted light from the lens which is illuminated by Ultra violet light; and a computer having an associated memory, an input for accepting the digital image output from said camera, and an output representative of an analyzed digital image wherein said analyzed digital image includes visible indications of any imperfections detected in said lens material.

This application is a divisional of U.S. Utility application Ser. No.15/355,595 filed on Nov. 18, 2016, which claims priority to SingaporeApplication No. 10201509497V filed on Nov. 18, 2015.

FIELD OF THE INVENTION

The present invention relates to an apparatus for inspecting defects inOphthalmic lenses suspended in containers filled with Saline solution.More specifically, the present invention relates to an apparatus andmethod to inspect the Ophthalmic lens quality using Ultravioletillumination.

BACKGROUND OF THE INVENTION

The present invention relates to an inspection system in an automatedproduction line. More particularly, the invention relates to a systemand method of inspection of ophthalmic lens that are illuminated withultraviolet light. The lenses are inspected in containers prior to thesealing process.

Ophthalmic lenses are packaged in small containers commonly called asblister packs. The containers typically contain a single ophthalmic lenssubmerged in saline solution. Prior art systems disclose inspectionsystems using LED illumination in the form of back light and frontlight. These type of inspection systems suffer from certain limitationsin detecting very fine cracks, bubbles and edge defects in the lensesdue to contaminated saline solution and bubbles in the solution thataffects the quality of inspection and increases the inspection timesignificantly as the software has to perform more analysis of the imageto differentiate between real and false defects. Furthermore, typicalLED illumination systems have difficulty in highlighting deformities inthe lens material, especially if the deformities are orientated alongthe axis of the illumination. Elaborate methods such as varying theillumination angle, changing the wavelength of the illumination combinedwith multiple images capturing have to be adopted to enable detailedanalysis of different images to detect very fine defects. In spite ofthese additional painstaking steps to detect fine defects, there areinstances, the inspection detects many good lenses as rejects whichincreases losses to the manufacturer. There are also instances whereinthe inspection system accepts defective lenses as good, in which casethe customer will encounter faulty lens.

It is a known phenomenon that certain fluorescent materials are capableof absorbing radiated electromagnetic energy in the near ultravioletspectrum and emitting it at a longer wavelength in the visible spectrumof light. This phenomenon enables various inspection of objectscomprising of fluorescent dyes or pigments, illuminated by anultraviolet radiation source that will re-radiate with luminescence inthe visible spectrum.

It is a well-known fact that fluorescent pigments or compounds are usedduring the manufacturing of contact lens. Typically fluorescentcompounds were utilized so laboratories could identify and detectmaterials and prevent duplication and identify counterfeits of the basematerial used in the manufacture of Contact lens. Counterfeiting andsubstitution of lens materials and misleading advertising had become acommon place. Fluorescence is a process of photo-luminescence by whichlight of short wavelengths, either in the ultraviolet or the visibleregions of the electromagnetic spectrum, is absorbed and re-radiated atlonger wavelengths. The re-emission occurs within the visible region ofthe light spectrum. The fluorescent compounds in the contact lensmaterial exhibit the phenomenon of fluorescing under ultraviolet light.The fluorescent light emanating from the pigment in the contact lensmaterial, is reflected within the polished optical surfaces of the lensand concentrated at the lens edge or any edge formed as a result of adefect or other deformity. The phenomena of fluorescing is especiallypronounced at the edges of the material and where the material is brokenor disrupted in its physical characteristics. No fluorescence is visiblewhen the material is illuminated with standard LED illumination or InfraRed illumination. However the fluorescence is obvious when the samematerial is illuminated using ultraviolet illumination. Accordingly,defects such as voids, bubbles or cuts within the material will appearas bright (pixels) on the digital image captured by the camera, sincelittle or no light in the fluorescent wavelength will be emitted fromthe section of the material representative of the defects. Accordingly,the present invention is particularly suited for detecting defects inpigmented lens material, even where those voids may be undetectable tothe naked eye.

An apparatus and methods are needed that can produce consistentlyenhanced images of contact lenses suspended in saline solution, toenable reliable and robust detection of edge defects, breakages andbubbles in the lenses. This is the objective of the present invention.

SUMMARY OF INVENTION

The apparatus and method of the present invention address at least someof the difficulties seen in the prior art.

It is an object of the present invention to provide an apparatus forinspecting contact lenses suspended in Saline solution to inspect edgesand any deformities within contact lenses. The invention providedconstitutes a high resolution camera and a lens to capture high qualityimages of the contact lens which is illuminated with UV light. The UVlight fundamentally excites the contact lens material or fluorescentpigments that exist within the contact lens material. The re-emittedlight, which is of a longer wavelength in the visible spectrum passesthrough an appropriate filter to prevent the camera from picking upstray and other spectrum of light.

It is further an object of the present invention to provide an apparatusand method to utilize the phenomenon of irradiation under ultraviolet(365 nm) wavelength illumination, for inspection of contact lensesdefects such as cuts, breakages and any deformities.

It is further an object of the present invention to provide an apparatusthat is integrated with an UV LED based illumination module enabled forelectronically controlling the illumination to emit light in short pulseat any given instance.

It is further an object of the present invention to provide an apparatusthat is integrated with an UV LED based illumination module enabled forelectronically controlling the intensity of the light to suit differentinspection criteria.

It is further an object of the present invention to provide an apparatusto enable strobing of the UV LED based illumination module, to maintaina very consistent and stable intensity of light from one pulse toanother.

In further an object of the present invention to provide an improvedmethod of inspecting contact lenses wherein the lenses are illuminatedwith Ultraviolet light and images are captured using a specificwavelength color filter (For eg: of 542 nm) positioned in front of theCamera lens.

It is further an object of the present invention to provide an apparatusto capture high resolution images of the contact lens to enable enhancedanalysis for detection of defects at the edges of the contact lens andwithin the area of the contact lens.

It is yet another aspect of the present invention to provide anapparatus for use as an inline inspection module that is easilyintegrated into an automated inspection system.

Other features and objects of the present invention will become apparentfrom the detailed description of the preferred embodiment(s) as well asthe drawing figures included herein below.

BRIEF DESCRIPTION OF DRAWINGS

It will be convenient to further describe the present invention withrespect to the accompanying drawings that illustrate possiblearrangements of the invention. Person skilled in the art will appreciatethat other arrangements of the invention are possible, and consequentlythe particularity of the accompanying drawings is not to be understoodas superseding the generality of the preceding description of theinvention.

FIG. 1 shows an illustration of the optical and illumination systemaccording to the present invention.

FIG. 2 shows an illustration of the optical and illumination system ofprior art.

FIG. 3 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 2 that incorporates astandard LED illumination module.

FIG. 4 shows an enlarged image of area B1 in FIG. 3.

FIG. 5 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 1 that incorporates aUltraviolet LED illumination module.

FIG. 6 shows an enlarged image of area B1 in FIG. 5.

FIG. 7 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 2 that incorporates astandard LED illumination module.

FIG. 8 shows an enlarged image of area B2 in FIG. 7.

FIG. 9 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 1 that incorporates aUltraviolet LED illumination module.

FIG. 10 shows an enlarged image of area B2 in FIG. 9.

FIG. 11 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 2 that incorporates astandard LED illumination module.

FIG. 12 shows an enlarged image of area B3 in FIG. 11.

FIG. 13 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 1 that incorporates aUltraviolet LED illumination module.

FIG. 14 shows an enlarged image of area B3 in FIG. 13.

FIG. 15 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 2 that incorporates astandard LED illumination module.

FIG. 16 shows an enlarged image of area B4 in FIG. 15.

FIG. 17 shows an image of ophthalmic lens of a defective lens at theedge, captured using the inspection system in FIG. 1 that incorporates aUltraviolet LED illumination module.

FIG. 18 shows an enlarged image of area B4 in FIG. 17.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIG. 1, and in accordance with a constructed embodiment ofthe present invention, a system 100 and method for detecting defects atthe edges, bubbles and breakages and other deformities within the lensmaterial includes a camera 220 having a lens 210 suitably integrated toa computer for analysis of the image captured by camera 220 as seenthrough the lens 210. The camera 220 may include an integral or detachedillumination module 130 that emits ultraviolet light synchronously withthe operation of a shutter or a strobe controlling electronics module(not shown), as is well known in the art.

Furthermore, in accordance with the present invention includes a firstoptical filter 110 is disposed over the lens 210 of the camera 220thereof such that any light entering the lens 210 must first passthrough the first optical filter 110. The first optical filter 110 isselected to block those wave lengths of light that include thewavelengths that excite the fluorescence of the contact lens 150, beinginspected. Thus the camera 220 obtains an image that includes the lightemitted through the effect of fluorescence but devoid of details fromthe spectrum of light rejected by the first optical filter 110. One ofordinary skill in the art will recognize that the placement of the firstoptical filter 110, whether in front of or behind the lens 210 of thecamera 220, does not affect the operation of the present invention.

Additionally, the present invention may incorporate an ultraviolet (UV)light source 130, or alternatively a plurality thereof, disposed in anarray around the lens 210 of the camera 220 in order to providecomprehensive UV light illumination of the inspection target at aplurality of incident angles. The UV light sources 130 may comprise aplurality of UV light emitting diodes (LEDs) emitting light at awavelength sufficient to excite fluorescent emission in the contact lens150 suspended in a saline solution 140 all of which are held in acontainer 120 being inspected. The container material 120 may include,but not limited to translucent or frosted plastic material.

In accordance with one embodiment of the present invention, the LEDsused to illuminate the contact lens may be selected to emit radiation inthe spectrum required to excite fluorescent emission for a given lensmaterial type. Accordingly, it is possible to either select a differentoptical filter to tailor the excitation light spectrum based on a UV LEDarray 210, or select an LED array to correspond to the requisiteexcitation light spectrum.

In a yet further embodiment of the present invention the UV LEDs basedillumination module may be energized to emit light synchronously withthe operation of the camera 220 in order to reduce the requisiteelectrical power required to operate the UV LEDs as well as extend theuseful life of the LEDs as well as to eliminate smear in the imagecapture. This may be accomplished by utilizing a commercial electronicstrobe controller (not shown) to deliver a programmed time pulse to theLED array synchronously with the camera 220 image acquisition process.

The camera 220 obtains an image that includes the light emitted by thelens 150 through the effect of fluorescence created as a result of theUV light source 130, but devoid of details from the spectrum of lightrejected by the first optical filter 110.

The apparatus in FIG. 2 relates to prior art commonly designed forinspecting defects in contact lenses. The apparatus 200 in FIG. 2differs from the apparatus 100 of the present invention shown in FIG. 1,where in the backlight or common LED illumination 160 of FIG. 2 ispositioned below the object of inspection 150 compared to the frontlight UV LED illumination 130 of FIG. 1 which is positioned on top ofthe object 150 to be inspected.

The foregoing detailed description of the embodiment(s) of the presentinvention is presented primarily for clearness of understanding and nounnecessary limitations are to be understood or implied therefrom.Modifications to the present invention in its various embodiment(s) willbecome obvious to those skilled in the art upon reading this disclosureand may be made without departing from scope of the inventionencompassed by the claims appended hereto. In view of the above, it willbe seen that the several objects of the invention are achieved and otheradvantages are obtained. As many changes could be made in the aboveconstructions and methods without departing from the scope of theinvention, it is intended that all matter contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

In a preferred embodiment of the present invention several examples aredescribed below.

FIG. 3 shows an image of an ophthalmic lens captured using apparatus 200illustrated in FIG. 2. As evident in FIG. 3, a probable defect is seenin the form of a broken edge in the area shown by box B1. An enlargedimage of the box B1 (FIG. 3) is shown in FIG. 4. The edge of theophthalmic is seen as a Black edge with a small and insignificant breakin the edge. Depending upon the inspection parameters, the edge in FIG.4 may or may not be detected as a defect. This ambiguity may result inthe Ophthalmic lens being inspected as a GOOD or BAD lens. More analysismay need to be done on the image which results in delayed inspectionresult.

FIG. 5 shows an image of the same ophthalmic lens of FIG. 3, but withthe image captured using apparatus 100 as illustrated in FIG. 1. Thearea indicated by box B1 in FIG. 5 is shown enlarged in FIG. 6. The edgeof the ophthalmic lens is seen as a white edge due to the florescencephenomenon when exposed to UV LED illumination utilized in apparatus100. It is evident that the white circular line representing the edge ofthe ophthalmic lens shows a non-continuous white line, indicating adefect at the edge of the lens. Further analysis by the software, thebreak in the white line indicating the edge in FIG. 6 of the lens isaccurately and consistently detected as a non-continuous edge.

FIG. 7 shows an image of an ophthalmic lens captured using apparatus 200illustrated in FIG. 2. As evident in FIG. 7, a probable defect is seenin the form of a bubble within the lens material in the area shown bybox B2. An enlarged image of the box B2 (FIG. 7) is shown in FIG. 8. Thebubble is seen as a round defect with at the edge of the lens. Dependingupon the inspection parameters, the bubble in FIG. 8 may or may not bedetected as a defect. This ambiguity may result in the Ophthalmic lensbeing inspected as a GOOD or BAD lens. More analysis may need to be doneon the image which results in delayed inspection result.

FIG. 9 shows an image of the same ophthalmic lens of FIG. 7, but withthe image captured using apparatus 100 as illustrated in FIG. 1. Thearea indicated by box B2 in FIG. 9 is shown enlarged in FIG. 10. Theedge of the ophthalmic lens is seen as a white edge due to theflorescence phenomenon when exposed to UV LED illumination utilized inapparatus 100. It is also evident that the semi-circular white circularline representing the edge of the bubble within the ophthalmic lens isvery prominent and can be reliably and repeatedly detected. It isimportant to note that on further analysis by software algorithms,measurements such as diameter of the bubble, any foreign particle etc.,is easily accomplished as the image is greatly enhanced.

FIG. 11 shows an image of an ophthalmic lens captured using apparatus200 illustrated in FIG. 2. The contact lens is positioned at a spot inthe container 120 wherein it coincides with the edge of the Salinesolution. As evident in FIG. 11, a bubble defect is observed in the areaB3. An enlarged image of the box B3 (FIG. 11) is shown in FIG. 12. Afaint bubble is seen very close to the black edge of the lens and theSaline solution. The bubble is seen as a round defect with at the edgeof the lens. Depending upon the inspection parameters, the bubble inFIG. 12 may or may not be detected as a defect. This ambiguity mayresult in the Ophthalmic lens being inspected as a GOOD or BAD lens.More analysis may need to be done on the image which results in delayedinspection result.

FIG. 13 shows an image of the same ophthalmic lens of FIG. 11, but withthe image captured using apparatus 100 as illustrated in FIG. 1. Thearea indicated by box B3 in FIG. 13 is shown enlarged in FIG. 14. Theedge of the ophthalmic lens is seen as a white edge due to theflorescence phenomenon when exposed to UV LED illumination utilized inapparatus 100. It is also evident that the semi-circular white circularline representing the edge of the bubble within the ophthalmic lens issignificantly enhanced without merging into the Saline Solutionbackground as observed in FIG. 12. The bubble in FIG. 14 is seamlesslydetected by the analysis software and furthermore it is repeatedly andconsistently located accurately to ensure assured quality of theinspected product.

FIG. 15 shows an image of an ophthalmic lens captured using apparatus200 illustrated in FIG. 2. As observed in FIG. 15, a probable crackdefect is seen in the box area B4. An enlarged image of the box B4 (FIG.15) is shown in FIG. 16. Some parts of the area in B4 shows a dark linewhich is discontinuous in certain parts and faint in other parts.Inspection of this defect can yield unreliable results.

FIG. 17 shows an image of the same ophthalmic lens of FIG. 15, but withthe image captured using apparatus 100 as illustrated in FIG. 1. Thearea indicated by box B4 in FIG. 17 is shown enlarged in FIG. 18. Thedefect seen in box B4 of FIG. 18 appears like a probable crack appearslike a prominent dark line when exposed to UV LED illumination utilizedin apparatus 100. It is also evident that the line is continuous withhigh contrast, which results in the defect being reliably and repeatedlydetected when analyzed by the inspection system.

Various modifications can be made without departing from the spirit ofthis invention or the scope of the appended claims. In view of theabove, it will be seen that the several objects of the invention areachieved and other advantages are obtained. A person skilled in the artwill be able to make many changes in the above apparatus and methodswithout departing from the scope of the invention. It is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

The invention claimed is:
 1. A system for detecting, defects in acontact lens including lens material having fluorescent materialtherein, comprising: a first ultra violet, light source to illuminatesaid lens with ultra violet light in a first color spectrum designed toexcite light emission by said lens material of light in a second colorspectrum caused by the fluorescent emission therein; a camera having alens and a digital image output for inspecting, said lens suspended insaline solution, wherein said camera's digital image output includesonly an image produced by light in the second color spectrum; a firstoptical filter positioned between the camera and said lens to filter theemitted light from the lens which is illuminated by Ultra violet light,said optical filter arranged to prevent the camera from picking up straylight and other spectrums of light; and a computer having an associatedmemory, an input for accepting the digital image output from saidcamera, and an output representative of an analyzed digital imagewherein said analyzed digital image includes visible indications of anyimperfections detected in said lens material; wherein the ultravioletlight from the ultra violet light source is arranged to excite thefluorescent material in said lens, such that the fluorescent materialappears white in said image captured by the camera.
 2. A system asclaimed in claim 1 wherein said light source comprises an array of UVlight emitting diodes.
 3. A system as claimed in claim 2 wherein saidarray of UV light emitting diodes is disposed around the lens of saidcamera.
 4. A system as claimed in claim 1 further comprising a strobecontroller capable of energizing said light source in synchronousoperation with the image acquisition of said camera.
 5. A system asclaimed in claim 4 further comprising a feature within the strobecontroller capable of energizing said light source with different timingpulses in synchronous operation with the image acquisition of saidcamera.